The physiological effects of drugs of abuse form associations with other stimuli present in the environment in which the drug is experienced. These associations play an integral role in the acquisition, maintenance, and relapse of drug-taking behavior. In human tobacco users nicotine is experienced in the presence of a variety of other stimuli. These other stimuli are often the object of behavioral treatments for smoking cessation. Therefore, a better understanding how nicotine interacts with other stimuli for control of a conditioned response may assist smoking cessation behavioral treatment strategies. The goal of the present proposal is to systematically examine cue competition between a discrete interoceptive nicotine CS and an exteroceptive light CS in an appetitive Pavlovian discrimination task. In Specific Aim 1 we will determine whether nicotine overshadowing of the light is dependent on nicotine dose. Rats will be trained using a compound stimulus in which the concurrent intravenous infusion of nicotine and a light presentation will be reliably followed by a brief sucrose delivery. Overshadowing will be determined by the relative control of conditioned responding by each of the elements when they are tested separately. We will also examine the blocking phenomenon between the exteroceptive light and interoceptive nicotine CSs. In Specific Aim 2, rats will be trained with either nicotine or the light paired reliably with the sucrose delivery. After acquisition of the conditioned response, the other element (i.e., nicotine infusion or light) will be added to create the compound conditioned stimulus. Again, rats will then be tested for control of conditioned responding to each element separately. We expect that the stimulus that is first paired with sucrose will block conditioned responding to the subsequently added stimulus. The findings of the proposed research will fill an important gap in our understanding of associative learning processes involving nicotine and may assist smoking cessation behavioral treatment strategies. [unreadable] [unreadable] [unreadable]